1. Field of the Invention
The present invention relates to a numerical controller having a function for displaying a trajectory of a representative point, such as a tool center point, of a machine tool.
2. Description of the Related Art
In the prior art, as a method for monitoring an error in a shape of a machined object, a tool trajectory displaying method has been used, wherein a commanded trajectory of a representative point (such as a tool center point) of a machine tool and a feedback trajectory obtained when the representative point is actually moved according to the command are overlapped and displayed so that an error of the feedback trajectory relative to the commanded trajectory is visually monitored. For example, Japanese Unexamined Patent Publication (Kokai) No. 2003-75472 discloses a technique for displaying two servo information waveforms based on servo information from a controller, wherein the two waveforms are overlapped with each other within a single display frame.
Japanese Unexamined Patent Publication (Kokai) No. 6-59717 discloses an NC device having a function for overlapping a movement trajectory of a tool generated by analyzing an NC program with positional data obtained when the tool is moved according to the movement path.
Japanese Unexamined Patent Publication (Kokai) No. 2006-227886 discloses a servo controller and a method of adjusting a servo system, and describes “a sine arc instruction is given to the servo system as a move instruction having periodicity. Position feedback data and data before one quarter cycle or after one quarter cycle or position data based on the position instruction before one quarter cycle or after one quarter cycle are converted into each position data of the X-axis and the Y-axis, and an obtained image is drawn on the two-dimensional plane (X-Y plane).”
Further, Japanese Unexamined Patent Publication (Kokai) No. 2011-22666 discloses an analyzing/editing device of an NC program, having means for displaying a tool trajectory and drawings of drilling and a workpiece, wherein the tool trajectory and the drawings are overlapped with each other.
In the prior art, since feedback trajectories, before and after changing a processing condition such as processing speed, cannot be displayed while being overlapped with each other, it is necessary to separately display each trajectory on different displays in order to visually compare the trajectories. Therefore, in the prior art, the difference of the trajectories between before and after changing the processing condition cannot be accurately evaluated.
For example, although Japanese Unexamined Patent Publication (Kokai) No. 2003-75472 discloses the overlapping with reference to a time axis, this document does not describe the overlapping of data, such as a tool trajectory, which does not depend on the time axis. Although Japanese Unexamined Patent Publication (Kokai) No. 6-59717 and Japanese Unexamined Patent Publication (Kokai) No. 2006-227886 disclose that the feedback trajectory is overlapped with the commanded trajectory, these documents do not describe that a plurality of feedback trajectories are overlapped with each other. Further, although Japanese Unexamined Patent Publication (Kokai) No. 2011-22666 discloses that the tool trajectory, the processed shape of the workpiece and the drilled workpiece are overlapped with each other, this document does not describe a method for overlapping a plurality of feedback trajectories with each other.